Golf ball

ABSTRACT

A golf ball is provided that has a hard sphere core or layer that exhibits a controlled vibrational response. The vibrational response may be controlled by tailoring the stiffness or damping of the sphere with at least one element, such as a groove(s) or any other type of indentation in the hard sphere core. The groove (or grooves) serves to locally reduce the wall thickness of the hollow metal sphere core, thereby reducing the stiffness of the core by allowing larger deformations under a load without significantly reducing the total mass of the core. This results in a golf ball that is legal for play and capable of drive distances essentially equivalent to those of currently available high performance golf balls, but that also maintains a high moment of inertia, allowing less hooks and slices during play.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 10/756,185, filed Jan. 13, 2004, which is a continuation ofU.S. Pat. No. 6,705,957, issued Mar. 16, 2004, which is a continuationof U.S. Pat. No. 6,004,225, issued Dec. 21, 1999, which claims priorityto U.S. Provisional Patent Application No. 60/036,196, filed Jan. 16,1997.

FIELD OF THE INVENTION

The present invention relates generally to an improved multi-piece golfball, and more particularly, a multi-piece golf ball including a hollowmetal sphere.

BACKGROUND OF THE INVENTION

Various types of regulation golf balls have been proposed. In order tomeet the United States Golf Association (“U.S.G.A.”) specifications, thegolf ball must be spherical in shape, have equal aerodynamic propertiesand equal moments of inertia about any axis through its center. The ballmust have a minimum diameter of 1.68 inches (4.267 centimeters), amaximum weight of 1.620 ounces (45.926 grams), and a maximum initialball velocity of 255 feet per second as measured on a standard U.S.G.A.ball testing machine.

Golf balls are generally of two kinds, a wound golf ball and a moldedgolf ball. Because molded golf balls are cheaper to produce and moredurable than conventional wound golf balls, efforts have been focused ondesigning molded balls to improve such characteristics as initialvelocity, number of revolutions, angle of departure, moment of inertia,and dimple form. Most golf balls presently manufactured are two-pieceballs of uniform density cores throughout.

More recent golf ball designs have, however, focused on solid,multi-piece golf balls wherein the density of the ball is not uniformthroughout. For example, U.S. Pat. No. 4,863,167 to Matsuki et al.discloses a three-piece molded golf ball which includes a centerportion, an outer layer disposed over the center portion, and a coverdisposed over the outer layer. The center and outer layers are formedfrom a rubber composition containing a base rubber. The rubbercomposition of the outer layer contains a gravity filler with a highspecific gravity such that the outer layer has a higher specific gravitythan the center of the solid core. The gravity filler may be selectedfrom tungsten, tungsten carbide, molybdenum, lead, lead dioxide, nickel,or copper.

Other golf ball designs consider both the weight or density distributionof the ball and the relative hardness of the various layers whichcomprise the golf ball. For example, U.S. Pat. No. 4,979,746 issued toGentiluomo discloses a two or three piece molded type golf ball havingan elastic center. The elastic center has a minimum compressibility ofat least ten percent greater than the contacting synthetic elastomercomposition which is highly resilient and has a minimum Shore Adurometer hardness of about 70. The softer elastic center such asplastic elastomer or rubber, plastic or rubber foam, natural orcomposition cork, allows each ball to flatten more under club impact, toreduce likelihood of ball breakage and provide for excellent click andfeel. When the center is made of low density material, more weight isallowed to be concentrated within the outer portion of the ball toprovide a ball exhibiting reduced hooking and slicing action whenimproperly hit.

U.S. Pat. No. 5,026,067 also issued to Gentiluomo discloses a regulationgolf ball comprising a low density center having a maximum diameter of1.25 inches, a molded encapsulating mass surrounding the center, whereinthe material in contact with the center is a highly resilient syntheticelastomer composition having a minimum Shore A durometer hardness of 70and a specific gravity of 1.0, and a patterned surface contouring ofpredetermined structure contained within the outer surface of the golfball. The center has a compressibility of less than ten percent of thecompressibility of the material in contact therewith, and a density lessthan the maximum prevailing density of the encapsulating mass.

U.S. Pat. No. 5,273,286 issued to Sun discloses a multiple concentricsection golf ball comprising four sections each having a spherical outersurface, and all sections having a common center. The first section isan inner core closest to the center and consists of substantiallyincompressible material. The second section is an intermediate coreconsisting essentially of carbonaceous material, and the third sectionis an outer core in the form of a shell surrounding the intermediatecore which consists essentially of an elastomer. The fourth section is acover in the form of a shell surrounding the outer core. The radius ofgyration and spin rate of the golf ball can be controlled by selectionof the weight, density, and size of each of the first, second and thirdsections.

More recently, U.S. Pat. No. 5,480,155 issued to Molitor et al.discloses a golf ball comprising a hollow, spherical shell of apolymeric material; a unitary, noncellular core of a material which, atthe time of introduction into the shell, is a liquid, and a one-piecespherical cover over the center. According to the specification, thespherical shell, as opposed to the core, is primarily responsible forthe high initial velocity obtained when the golf ball is struck by agolf club so as to allow the golf ball to be driven long distances. Thepreferred shell compositions are ionomers. Preferably, the core materialhas a specific gravity greater than that of the shell.

Except for the ball disclosed in Molitor, the above designs provide fora golf ball wherein the solid core of the golf ball becomes heaviercloser to the cover of the ball to improve the moment of inertia therebyimproving the spin and flight characteristics. While others haveattempted to provide golf ball designs so that the moment of inertia andthe spin rate can be controlled by selection of the weight or densityand size of the materials comprising the golf ball, these designs arelimited in the degree to which the higher density can be concentratedclose to the cover or outer edge of the golf ball. Additionally, the useof fillers such as zinc oxide, barium sulfate, calcium carbonate, andother non-polymer compounds to increase the weight distribution of theball toward the outer core adversely affect other important performancecharacteristics such as rebound.

Therefore, a golf ball design having a much improved moment of inertiaover current golf ball designs which allows the ball to possess improvedperformance characteristics of low spin for maximum distance whilemaintaining optimum rebound characteristics is desired.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a golfball with an improved moment of inertia by minimizing the density in thecenter of the ball while maximizing the density away from the center andnear the cover or outer edge of the ball, thereby allowing the ball topossess simultaneously the characteristics of low spin for maximumdistance and “bite” when landing on a surface such as a putting green.

It is another object of the present invention to provide a golf ballwith an improved moment of inertia without adversely affecting therebound characteristics.

It is yet another object of the present invention to provide a golf ballhaving improved performance characteristics such as “feel” and flighttrajectory.

These and other objects are provided, according to the presentinvention, by a golf ball having improved driving characteristics whichincludes a hard hollow sphere and an outer layer surrounding the sphere.In a preferred embodiment, a second layer is placed between the sphereand outer layer so that the second layer surrounds the sphere and issurrounded by the cover.

According to one advantageous embodiment, the sphere consists of ametal, including a metal alloy or an intermetallic, having a specificgravity ranging from about 2.5 to 20 and more preferably about 4.0 to11.0 and a diameter ranging from about 0.39 to 1.5 inches (1.0 to 3.8centimeters). The thickness of the sphere wall is about 0.020 to 0.25inches (0.05 to 0.64 centimeters) and more preferably about 0.02 to 0.08inches (0.05 to 0.20 centimeters). A metal such as titanium, having aspecific gravity of about 4.5, is preferred although other metals oralloys falling within the specific gravity range of about 2.5 to 20 andmore preferably about 4 to 11 may be used. Alternatively, a hard plasticor other similar material, such as polypropylene which does notappreciably deform under loads usually placed on a golf ball, may beused to form the hard sphere. Where a hard plastic is used, the specificgravity of the sphere ranges from about 0.8 to 2.0. The plastic spheremay have a thickness of about 0.05 to 0.5 inches (0.13 to 1.27centimeters).

In another embodiment, a second layer is disposed between the sphere andcover. The second layer preferably consists of a synthetic polymercompound such as polybutadiene, a natural rubber compound, or acombination thereof. The thickness of the second layer is about 0.05 to0.65 inches (0.13 to 1.65 centimeters) and more preferably about 0.21 to0.55 inches (0.53 to 1.4 centimeters). The second layer is preferablysurrounded by a cover material with a surface dimple pattern as iswell-known in the art. The cover typically consists of the materialselected from the group consisting of an ionomer, urethane, balata, orsynthetic elastomer. Examples of ionomers include material sold underthe trade name SURLYN, produced by DuPont Company, or under the tradename IOTEK, produced by Exxon Company. According to another preferredembodiment, the hollow sphere may contain either residual gas, such asair, or a gas at any pressure. The hollow sphere may also contain asolid or liquid material having a density that is less than the densityof the outer cover.

Therefore, according to the present invention, a golf ball with improvedperformance characteristics is provided. In particular, the golf ballcontains a hard sphere surrounded by a second layer of compressiblematerial such as polybutadiene. The second layer is then covered by amore durable material such as an ionomer. Thus, the golf ball of thepresent invention concentrates the weight and, therefore, the densityaway from the center of the ball to improve its performancecharacteristics while maintaining optimum rebound characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional perspective view of the golf ball ofthe present invention.

FIG. 2 is a cross-sectional view of a three-piece golf ball of thepresent invention shown in FIG. 1 wherein a second layer is placedbetween the sphere and the outer layer.

FIG. 3 is a cross-sectional view of a two-piece golf ball of the presentinvention having a hard sphere surrounded by an outer layer.

FIG. 4 is a cross-sectional view of the three-piece golf ball of thepresent invention which has a solid or liquid material inside of thesphere.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which a preferred embodimentof the invention is shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiment set forth herein; rather, this embodiment is provided so thatthis disclosure will be thorough and complete, and will fully convey thescope of the invention to those skilled in the art. Like numbers referto like elements throughout.

The inventors of the present invention have discovered that a golf ballcomprising a hard hollow sphere increases the moment of inertia andreduces spin, thereby increasing distance. In addition, the golf ball ofthe present invention provides increased spin retention, i.e. “bite”.The golf ball therefore combines the favorable characteristics ofexisting two-piece and three-piece balls, i.e. distance and “bite.”Furthermore, the inventors have discovered that a hollow metal spherehas excellent rebound properties which, when incorporated into a golfball, can improve its performance.

Referring now to FIGS. 1 and 2, an improved golf ball according to oneembodiment of the present invention is illustrated. The golf ball 11includes a hard, hollow sphere 13 surrounded by a second layer 14. Thesecond layer is then surrounded by an outer cover 15.

The sphere 13 is preferably made of a hard material having a specificgravity ranging from about 2.5 to 20 and more preferably from about 4 to11, an outside diameter ranging from about 0.39 inches to 1.50 inches(about 1.0 to 3.8 centimeters), and a thickness of about 0.02 to 0.25inches (0.05 to 0.64 centimeters) and more preferably about 0.02 to 0.08inches (0.05 to 0.20 centimeters). The hard material comprising thesphere may be any metal such as titanium, a titanium alloy, or othermetal alloy including stainless steel, or an intermetallic material suchas titanium and aluminum. The metal may also be iron, carbon steel,nickel, molybdenum, aluminum, tungsten or alloys of steel, nickel,aluminum, molybdenum, or tungsten. The metal comprising the sphere mayhave a Brinnell hardness of greater than 40.

Alternatively, the hard material may be a plastic which does notappreciably deform under loads usually placed on a golf ball such aspolypropylene in which case the specific gravity is about 1.0. Ifplastic, the hollow sphere may have a thickness of about 0.05 to 0.5inches (0.13 to 1.27 centimeters). The plastic comprising the sphere mayhave a Shore D hardness of greater than 60. The metal or plastic ispreferably solid but may also be perforated or porous. A ceramic,including silicon carbide may be used. The sphere improves the moment ofinertia of the ball, thereby reducing spin, by moving the mass away fromthe center of the ball. The diameter, thickness, and specific gravity ofthe sphere will vary depending on specific design parameters, includingspin rate, feel or rebound, and materials used in construction of theball.

The second layer 14 is preferably of a compressible, resilient material,including natural rubber or synthetic polymer compounds or a combinationthereof which is typically used in the manufacture of golf balls.Examples of such synthetic polymer compounds are polybutadiene, whichhas a specific gravity of about 1.15, polyisoprene, andstyrene-butadiene. Crosslinking or co-crosslinking agents may be addedto the rubber comprising the second layer to control its hardness andthus deformation and elastic recovery properties as is well-known in theart. High gravity fillers as are also well known in the art may also beadded to the rubber compound comprising the second layer. By usinghollow sphere 13 to increase the moment of inertia, however, fillers canbe minimized or eliminated from the second layer 14 altogether therebyallowing the use of softer rubber compounds in the second layer toimprove rebound characteristics. The second layer 14 may be wound ormolded construction. The second layer generally has an outside diameterof about 1.52 to 1.56 inches (3.86 to 3.96 centimeters) and a thicknessof 0.05 to 0.65 inches (0.13 to 1.65 centimeters) and more preferablyabout 0.21 to 0.55 inches (0.53 to 1.4 centimeters). The outer cover 15may be an ionomer, urethane, balata, or synthetic elastomer. The outercover also includes a dimple pattern as is well-known in the art.

Yet another embodiment of the improved golf ball 11 according to oneembodiment of the present invention is illustrated in FIG. 3. The golfball 11 includes a hard sphere 13, as described above, surrounded by anouter cover 15 without a intermediate second layer. The sphere ispreferably a metal, and more preferably titanium or stainless steel.This embodiment provides the greatest moment of inertia, less spin,greater rebound and, therefore, greater distance.

In a preferred embodiment of the invention as shown in FIG. 2, thehollow sphere 13 is not filled with any solid or liquid material. Thus,the hollow sphere contains a residual gas 12, preferably air. The hollowsphere may also contain pressurized gas. Preferably, the gas fills orsubstantially fills the hollow sphere. In another embodiment as shown inFIG. 4, the hollow sphere may contain a solid or liquid-based material12 a. Preferably, any solid or liquid material which may be placedinside the sphere is of lower density than the material comprising thesecond layer or outer cover surrounding the sphere in order to increasethe moment of inertia of the ball. Suitable solid materials may includenatural rubber or synthetic polymer, cork, or plastics. Suitable liquidmaterials include water and oil. Vegetable or mineral oils may be used.If a solid material is used, the solid material may be comprised oflayers of different materials. The outer cover 15 may be an ionomer,urethane, balata, or synthetic elastomer. The outer cover also includesa dimple pattern as is well known in the art.

Preferably, the golf ball 11 of the present invention has a minimumdiameter of 1.68 inches, a maximum weight of 1.620 ounces, and a maximuminitial ball velocity of 255 feet per second as measured on a standardU.S.G.A. ball testing machine.

The golf ball 11 may be made using conventional processes and techniquesas are presently employed in the art such as molding so that the ballwill be spherical in shape, have equal aerodynamic properties, and haveequal moments of inertia about any axis through its center. If plastic,the hollow sphere 13, may be made by techniques, such as blow molding,which are well-known in the art. If metal, the hollow sphere 13 may bemanufactured by forming two halves of a sphere by hot forming or coldforming which are then joined together by welding or other meanssufficient to securely join the halves of the sphere together. Methodsof forming two halves of a metal sphere include stamping, hydroforming,metal spinning, and superplastic forming as are well-known in the art.Methods of securely joining two halves of a metal sphere include welding(such as electron beam welding, laser welding, and electrical resistancewelding) or metal gluing as are well-known in the art. Metal spheressuitable for use according to the present invention can be obtained fromIndustrial Tectonics, located in Dexter, Mich. The outer layer and, ifdesired, the second layer are molded around the sphere using techniquesthat are well-known in the art. Alternatively, the second layer, or anyadditional layers, may be wound as is well-known in the art.

Examples of golf balls made according to the present invention are shownbelow:

EXAMPLE 1

Two Piece ball—Titanium core and SURLYN (manufactured by DuPont andregistered tradename) cover according to the following specifications:

A hollow sphere comprising a titanium shell with an inside diameter of1.374 inches (3.490 centimeters), outside diameter of 1.521 inches(3.863 centimeters), and a mass of 1.258 ounces (35.69 grams).

SURLYN cover with a density of 58.68 lb/ft.sup.3 (0.95 grams/cm3), aninside diameter of 1.521 inches (3.863 centimeters), an outside diameterof 1.680 inches (4.267 centimeters) and a mass of 0.3514 ounces (9.962grams). The residual gas in the core does not contribute significantlyto the mass of the ball. The total mass of the ball is 1.610 ounces(45.65 grams). The moment of inertia of the ball of Example 1 is about34 percent greater than a typical two-piece ball.

EXAMPLE 2

Three piece ball—Titanium core, second layer of polybutadiene, and aSURLYN cover:

A hollow sphere comprising a titanium shell with an inside diameter of0.992 inches (2.52 centimeters) and an outside diameter of 1.102 inches(2.80 centimeters), a specific gravity of 4.5 and a mass of 0.494 ounces(14.0 grams).

Polybutadiene (specific gravity=1.15) with a layer thickness of 0.210inches (0.53 centimeters) and a mass of 0.762 ounces (21.61 grams).

SURLYN (specific gravity=0.95) cover of thickness 0.0787 inches (0.2centimeters), and a mass of 0.348 ounces (9.87 grams).

The residual gas inside the core does not contribute significantly tothe mass of the ball. The total mass of the ball is 1.604 ounces (45.5grams). The moment of inertia of the ball of Example 2 is about sixpercent greater than a typical two-piece ball.

As described above, the improved golf ball of the present inventionprovides improved performance characteristics including low spin rate,long distance, and bite without adversely affecting reboundcharacteristics. The ball of the present invention minimizes hook andslice when improperly hit. The design of the golf ball allows variationsin the material and the size of the sphere, second layer, and outercover in order to optimize performance characteristics.

In the drawings and specification there has been set forth preferredembodiments of the invention and although specific terms are employed,the terms are used in a generic and descriptive sense only and not forthe purpose of limiting the scope of the invention being set forth inthe following claims.

1. A golf ball, comprising: a) an outer cover having an outer surface,wherein said outer surface has a dimpled pattern; and b) a single metalsphere disposed within said outer cover, said metal sphere defining awall formed of a metal having a thickness of at least 0.02 inches. 2.The golf ball of claim 1, wherein the metal is selected from the groupconsisting of titanium and titanium alloys.
 3. The golf ball of claim 1,wherein the metal is selected from the group consisting of stainlesssteel and steel alloys.
 4. The golf ball of claim 1, wherein the metalis tungsten.
 5. The golf ball of claim 1, wherein the metal is aluminum.6. The golf ball of claim 1, wherein the metal is molybdenum.
 7. Thegolf ball of claim 1, wherein the metal is nickel.
 8. The golf ball ofclaim 1, wherein the metal has a Brinnell hardness of greater than 40.9. The golf ball of claim 1, wherein the single metal sphere comprisestwo hemispherical portions each formed by stamping, said portions ofsaid sphere being fixedly secured together to form said single sphere.10. The golf ball of claim 1, wherein the single metal sphere comprisestwo hemispherical portions each formed by superplastic forming, saidportions of said sphere being fixedly secured together to form saidsingle sphere.
 11. The golf ball of claim 1, wherein the single metalsphere comprises two spherical portions each formed by metal spinning,said portions of said sphere being fixedly secured together to form saidsingle sphere.
 12. The golf ball of claim 9, wherein said portions ofsaid sphere are fixedly secured together by welding.
 13. The golf ballof claim 12, wherein said welding is electron beam welding.
 14. The golfball of claim 12, wherein said welding is laser welding.
 15. The golfball of claim 12, wherein said welding is electrical resistance welding.16. The golf ball of claim 9, wherein said portions of said sphere arefixedly secured together by glueing.
 17. The golf ball of claim 10,wherein said portions of said sphere are fixedly secured together bywelding.
 18. The golf ball of claim 17, wherein said welding is electronbeam welding.
 19. The golf ball of claim 17, wherein said welding islaser welding.
 20. The golf ball of claim 17 wherein said welding iselectrical resistance welding.
 21. The golf ball of claim 10, whereinsaid portions of said sphere are fixedly secured together by glueing.22. The golf ball of claim 11, wherein said portions of said sphere arefixedly secured together by welding.
 23. The golf ball of claim 22,wherein said welding is electron beam welding.
 24. The golf ball ofclaim 22, wherein said welding is laser welding.
 25. The golf ball ofclaim 22, wherein said welding is electrical resistance welding.
 26. Thegolf ball of claim 11, wherein said portions of said sphere are fixedlysecured together by glueing.
 27. The golf ball of claim 1, wherein saidmetal sphere contains a liquid material.
 28. The golf ball of claim 1,wherein said metal sphere contains a solid material.
 29. The golf ballof claim 1, wherein said metal sphere contains a gas.
 30. The golf ballof claim 1, having a moment of inertia in the range of from about 77gcm² to about 105 gcm².
 31. The modern golf ball of claim 1, having amoment of inertia in the range of from about 81.6 gcm² to about 103.2gcm².
 32. The golf ball of claim 1, having a moment of inertia of about82.8 gcm².
 33. The golf ball, comprising: (a) a one-piece metal sphereformed by welding two spherical metal portions together to define ahollow portion within said metal sphere; and (b) a cover layersurrounding said one-piece metal sphere.
 34. The golf ball of claim 33,wherein said one-piece metal sphere has an outside diameter of fromabout 0.39 to about 1.5 inches.
 35. The golf ball of claim 33, whereinsaid welding is electron beam welding.
 36. The golf ball of claim 33,wherein said welding is laser welding.
 37. The golf ball of claim 33,wherein said welding is electrical resistance welding.
 38. The golf ballof claim 33, wherein said hollow portion contains a gas.
 39. The golfball of claim 33, wherein said hollow portion contains a solid material.40. The golf ball of claim 33, wherein said hollow portion contains aliquid material.
 41. The golf ball of claim 33, wherein said sphericalmetal portions are formed by stamping.
 42. The golf ball of claim 33wherein said spherical metal portions are formed by superplasticforming.
 43. The golf ball of claim 33,wherein said spherical metalportions are formed by metal spinning.
 44. A golf ball comprising: (a) aone-piece metal sphere formed by welding two spherical metal portionstogether to define a hollow portion within said metal sphere; and (b) asecond layer surrounding said one-piece metal sphere.
 45. The golf ballof claim 44, wherein said one-piece metal sphere has a diameter of fromabout 0.39 to about 1.5 inches.
 46. The golf ball of claim 44, whereinsaid one-piece metal sphere has a thickness of at least 0.02 inches. 47.The golf ball of claim 44, wherein said welding is electron beamwelding.
 48. The golf ball of claim 44, wherein said welding is laserwelding.
 49. The golf ball of claim 44, wherein said welding iselectrical resistance welding.
 50. The golf ball of claim 44, whereinsaid hollow portion contains a gas.
 51. The golf ball of claim 44,wherein said hollow portion contains a solid material.
 52. The golf ballof claim 44, wherein said hollow portion contains a liquid material. 53.The golf ball of claim 44, wherein said spherical metal portions areformed by stamping.
 54. The golf ball of claim 44, wherein saidspherical metal portions are formed by superplastic forming.
 55. Thegolf ball of claim 44 wherein said spherical metal portions are formedby metal spinning.
 56. A golfball comprising a metal hollow sphere,wherein the hollow has a diameter in the range of from about 0.19 inchesto about 1.374 inches.
 57. The golfball of claim 56, wherein the hollowhas a diameter in the range of from about 0.9 inches to about 1.0 inch.58. The golfball of claim 57, wherein the hollow has a diameter of about0.958 inches.
 59. A golfball comprising a hollow metal sphere having amoment of inertia in the range of from about 77 gcm² to about 105 gcm².60. The golfball of claim 58, having a moment of inertia in the range offrom about 81.6 gcm² to about 103.2 gcm².
 61. The golfball of claim 58,having a moment of inertia of about 82.8 gcm².